Question

Brenda says a good estimate for 50× 31 3/4 is 800. is this correct? Explain.

Answer 1

No, it would not be a good estimate.If you make 31 3/4 into 32 then multiply 50x32 you get 1,600

Answer 2

At first glance, it seems like a good estimate; big numbers make bigger number.
But, this is multiplication, which means big numbers will make an extraordinarily big number, in proportion to the numbers themselves.
If you round 31 3/4 up to 32, you can multiply that by 50. To make the estimate easier, multiply 50 by 2,
50 x 2 = 100
Take the zeros off 50 and 30 to make this a bit simpler, and multiply 5 by 3,
5 x 3 = 15
Add each of the zeros you took off to the 15 to make 1500 (1 zero was taken off 50, and 1 off of 30),
And then add 1500 to that other 100
1500 + 100 = 1600
A good estimate for 50 x 31 3/4 would be 1600, not 800.
Therefore,
No. Brenda's estimate of 800 is NOT a good estimate.